Most "efficient" cartridge for each caliber?

[Newtosavage]

While prepping loads for my .284 Winchester the other day, a question popped up in my mind. I wonder what the most "efficient" cartridge is for each caliber, or if there even is one?

Reason I wonder this is because IMO the 7mm-08 (and 7x57 before it) are arguably the most efficient of the 7mm cartridges, in the sense that you get the best velocity to powder ratio for typical 7mm weight bullets. Or maybe not "the best" but it sure seems so.

It seems like as you go up in case size, the incremental gains in velocity get smaller in smaller. You can already see this going from the 7mm-08 to the .284 Winchester. It takes 7-10 grains more powder to deliver just 100-150 fps. more velocity. When you compare those to the 7mm Magnum, this seems even more true - a narrowing gap between powder spent and velocity earned.

So I wonder if there is a "most efficient" cartridge for each bore size, and if so, what is it? Surely with all the various rounds developed for each bore, one could map this out if not from real world experience, then just academically from published load data.

I suspect there might be a "most efficient for X range of bullet weights" winner in each caliber. IOW, where the 7mm-08 might be the most efficient cartridge for 120-140 grain bullets, it may not be for 160+ grainers. And so on.

Has this been done? If so, where could I find this list?

 

[someguy2800]

Lets compare 22 calibers since there is a huge range of sizes. I'll just use the fastest load for each listed in the hodgdon load data for a 50 grain bullet along with the listed powder weight.

22 swift, 4035 fps, 45.0 grains, = 89.6 fps per grain, 40.1 ft lbs per grain
22-250, 4001 fps, 43 grains, = 93.0 fps per grain, 41.3 ft lbs per grain
22 nosler, 3731 fps, 34.5 grains = 108.1 fps per grain, 44.78 ft lbs per grain
223 rem, 3505 fps, 28.5 grains = 122.9 fps per grain, 47.8 ft lbs per grain
221 fireball, 3202 fps, 19.8 grains = 161.7 fps per grain, 57.4 ft lbs per grain
22 hornet, 2713 fps, 13 grains = 208.7 fps per grain, 62.8 ft lbs per grain
22 magnum, (federal 50gr small game), 1530 fps, 5.2 grains = 288.6 fps per grain, 50 ft lbs per grain
22lr, (american eagle suppressor 45gr RN), 970 fps, 1.0 grains = 970 fps per grain, 94 ft lbs per grain

So even all the way down to 22lr we are still gaining efficiency. The only real outlier is the 22 magnum energy per grain, but that is because it runs at half the pressure of the centerfire rounds so the efficiency gain of being smaller wasn't enough to overcome the efficiency loss of being at a lower pressure.

 

[someguy2800]

Oh, and welcome back!

 

[Newtosavage]

Oh, and welcome back!

Ha! Thanks!

It's winter time so I'm reloading, spending time at the range, and tinkering with rifles again.

So I wonder if all cartridges follow that same trend, that efficiency (using this measure) increases as the case size decreases?

 

[denton]

When the bullet uncorks the barrel, the energy stored in the compressed gas behind it is lost to propulsion. The lower the pressure at bullet exit, the higher the efficiency.

 

[someguy2800]

I'm certain it would, so the smallest and shortest cartridge case that is capable of holding enough powder to reach your velocity target for a specific bullet will be the most efficient, assuming they are all the same pressure. I know there are some small efficiency gains to be had from shoulder angles and length.

 

[Newtosavage]

I'm certain it would, so the smallest and shortest cartridge case that is capable of holding enough powder to reach your velocity target for a specific bullet will be the most efficient, assuming they are all the same pressure. I know there are some small efficiency gains to be had from shoulder angles and length.

I suppose that's as good a way to look at this question as anything. First determine your bullet and required velocity, then go seek out a "house" for it to live in.

That's pretty well what I did with my .284 Win when I built it, even though I already had a 7mm-08 that I liked a lot.

 

[Varminterror]

Change powder type and bullet weight and efficiencies within given cartridges swing wildly.

Honestly, I have NEVER found any shooting application for which I truly gave a damned about efficiency. Using less powder is nice, but using a smaller “more efficient case” almost always describes some limitation which cannot be overcome by the smaller case. Be it hunting, plinking, competition, or HD/SD, I’ve never been compelled to collect ejecta residual and measure efficiency of combustion - the objective is achieving the velocity necessary to do the work required done at the distance at which it needs to be done, and finding a cartridge which does so with simple and forgiving load development is gravy.

In other words, I’ve never had combustion efficiency influence my success in a given application - ever, at all. However, I have had gross performance of given cartridges fall flat, and have had cartridges which were significantly more difficult to tune and develop loads which shot well - THOSE THINGS AFFECT MY LIFE. “Efficiency” really doesn’t affect anything I’ve ever done with a firearm, except elicit conversations like this online.

 

[Newtosavage]

Change powder type and bullet weight and efficiencies within given cartridges swing wildly.

Honestly, I have NEVER found any shooting application for which I truly gave a damned about efficiency. Using less powder is nice, but using a smaller “more efficient case” almost always describes some limitation which cannot be overcome by the smaller case. Be it hunting, plinking, competition, or HD/SD, I’ve never been compelled to collect ejecta residual and measure efficiency of combustion - the objective is achieving the velocity necessary to do the work required done at the distance at which it needs to be done, and finding a cartridge which does so with simple and forgiving load development is gravy.

In other words, I’ve never had combustion efficiency influence my success in a given application - ever, at all. However, I have had gross performance of given cartridges fall flat, and have had cartridges which were significantly more difficult to tune and develop loads which shot well - THOSE THINGS AFFECT MY LIFE. “Efficiency” really doesn’t affect anything I’ve ever done with a firearm, except elicit conversations like this online.

Me either. This is just a winter time rainy day academic exercise for my own edification. Those who already know this or simply don't care, are free to ignore the discussion.

 

[CoalTrain49]

Me either. This is just a winter time rainy day academic exercise for my own edification. Those who already know this or simply don't care, are free to ignore the discussion.

I thought it was a fun little game for a dreary winter day. Efficiency can be measured lots of different ways. If I hook up a 5K trailer to F-150 gas and compare my mileage to an F-250 diesel the F-250 is more fuel efficient. When overall cost per mile is measured it might be different. A Power Stroke F-250 costs a lot more than an F-150.

 

[Newtosavage]

I wonder if recoil impulse should be factored in to the "efficiency" measurement. IOW, what do you have leaving the barrel vs. what you have to tolerate to get it.

 

[Varminterror]

I wonder if recoil impulse should be factored in to the "efficiency" measurement. IOW, what do you have leaving the barrel vs. what you have to tolerate to get it.

The multivariate system we’re considering here can’t be nailed down. Rifle weight, recoil, bullet weight, powder selection, powder mass, operating pressure, muzzle velocity, expansion ratio, barrel length, etc etc etc… The analysis becomes an empty set because no conclusion can be truly drawn.

As a trend, smaller cases use less powder per fps, as illustrated above, however, you’re also losing gross performance - less and less muzzle velocity for a given barrel length - as you shrink the cases, OR you’re slamming higher and higher operating pressures and slower and slower powders in longer and longer barrels and heavier and heavier bullets… so the academic exercise is self defeating - the set becomes empty, because we shrink cases to a point where there no longer remains any relevancy for real world applications. Described by the e table @someguy2800 produced above - yes, you can increase efficiency by shrinking the case, but you leave behind a 220 Swift at 4000fps+ and pick up a 22LR, with obviously lesser ability in field application.

 

[Alaskan Ironworker]

Also, generally speaking for myself, the bigger the cartridge, the less rounds get fired. I’d be willing to bet i’ve burned more powder in my lifetime shooting .22 lr than anything else.

 

[2ndtimer]

I’m just happy to see a post from someone who recognizes the difference between “caliber” and “cartridge”.

 

[Newtosavage]

The multivariate system we’re considering here can’t be nailed down. Rifle weight, recoil, bullet weight, powder selection, powder mass, operating pressure, muzzle velocity, expansion ratio, barrel length, etc etc etc… The analysis becomes an empty set because no conclusion can be truly drawn.

As a trend, smaller cases use less powder per fps, as illustrated above, however, you’re also losing gross performance - less and less muzzle velocity for a given barrel length - as you shrink the cases, OR you’re slamming higher and higher operating pressures and slower and slower powders in longer and longer barrels and heavier and heavier bullets… so the academic exercise is self defeating - the set becomes empty, because we shrink cases to a point where there no longer remains any relevancy for real world applications. Described by the e table @someguy2800 produced above - yes, you can increase efficiency by shrinking the case, but you leave behind a 220 Swift at 4000fps+ and pick up a 22LR, with obviously lesser ability in field application.

Certainly, but we each could establish some values that narrow down the list of variables.

For instance, I know that once the ft. lbs. of recoil approach 20-21, I start to notice it and react to it. I also know that bullet weights below 100 grains or over 180 grains don't really serve much purpose for the game I typically pursue...etc.

By establishing a few limits, one could quickly narrow down the results.

 

[someguy2800]

Certainly, but we each could establish some values that narrow down the list of variables.

For instance, I know that once the ft. lbs. of recoil approach 20-21, I start to notice it and react to it. I also know that bullet weights below 100 grains or over 180 grains don't really serve much purpose for the game I typically pursue...etc.

By establishing a few limits, one could quickly narrow down the results.

Efficiency also goes up as the bore diameter increases for either a given bullet weight, or for a given powder charge weight. So if you give a parameter of 180 grain maximum weight and 21 ft lbs max recoil energy, you will just get a straight wall case in the largest reasonable caliber. Obviously though the ballistics on that will suck so you would also need to specify as a condition that you want a certain performance at a certain range in order to also take ballistic coefficient into account. Say instead of looking for muzzle energy or velocity, say you want the minimum of XXXX ft lbs of energy at 300 yards with the least free recoil energy.

You would have to run literally millions of calculations to cover all the possible bullet, powder, and cartridge combinations that are possible, unless you had a computer program to run them all for you, but if you nail it down to a specific case size, and just calculate it out for maybe 2 or 3 loadings in each caliber you can probably plot a general trend. Say if you take 243, 260, 7-08, 308, 338 fed, and 358 win mag and pick a couple loads for each and run it through a ballistic calculator at 300 yards, and a free recoil calculator. I know they make a nosler accubond in all of those calibers so to give each one the fairest comparison you could compare that bullet in all of them and see what you find.

 

[Newtosavage]

Efficiency also goes up as the bore diameter increases for either a given bullet weight, or for a given powder charge weight. So if you give a parameter of 180 grain maximum weight and 21 ft lbs max recoil energy, you will just get a straight wall case in the largest reasonable caliber. Obviously though the ballistics on that will suck so you would also need to specify as a condition that you want a certain performance at a certain range in order to also take ballistic coefficient into account. Say instead of looking for muzzle energy or velocity, say you want the minimum of XXXX ft lbs of energy at 300 yards with the least free recoil energy.

You would have to run literally millions of calculations to cover all the possible bullet, powder, and cartridge combinations that are possible, unless you had a computer program to run them all for you, but if you nail it down to a specific case size, and just calculate it out for maybe 2 or 3 loadings in each caliber you can probably plot a general trend. Say if you take 243, 260, 7-08, 308, 338 fed, and 358 win mag and pick a couple loads for each and run it through a ballistic calculator at 300 yards, and a free recoil calculator. I know they make a nosler accubond in all of those calibers so to give each one the fairest comparison you could compare that bullet in all of them and see what you find.

I wonder if someday, someone will have all this worked out on a plug and play app, with sliders so you can adjust your parameters and it will spit out a recommended cartridge, bullet, powder combo. People are so eager to build apps these days, it wouldn't surprise me if someone did something like this, if even just to compare cartridges against one another.

 

[jmr40]

I don't know about most efficient, but efficiency plays a role in my choosing cartridges. But it didn't always. I hunted with 30-06 for the better part of my life, about 40 years. But about a dozen years ago moved to 308. Looking at some numbers, (my actual loads).

I can get 2900 fps with 150's using 47 gr of powder in my 308

I can get 3050 fps with 150's using 62 gr of powder in my 30-06. Thats about 4% more speed, 24% more powder and about 20% more recoil.

I can get 3300 fps with 150's using 80 gr of powder in a 300 WM. Compared to 308 that is 12% more speed, 42% more powder and almost double the recoil.

When you start looking at trajectory, retained velocity, and energy numbers down range the 30-06 and 300 WM don't offer me any real advantages until I start taking shots beyond 400-500 yards. Which is farther than I'm going to shoot anyway.

I sold the 300 WM and keep the 30-06 simply because it has too much history to sell. But I rarely shoot it anymore and every time I sit down to load for it the amount of powder I'm pouring into each case just seems huge compared to what I load in my 308 cases. That same pound of powder just goes a lot farther.

Now if someone NEEDS the power and has the skills to use it then you NEED to go with a less efficient cartridge. A 3/4 ton truck with a diesel engine isn't as efficient as a Prius. But if you need to move a load the Prius won't get it done.

 

[someguy2800]

I wonder if someday, someone will have all this worked out on a plug and play app, with sliders so you can adjust your parameters and it will spit out a recommended cartridge, bullet, powder combo. People are so eager to build apps these days, it wouldn't surprise me if someone did something like this, if even just to compare cartridges against one another.

yeah it would be neat, even if it only used published factory ammo data

 

[Varminterror]

I wonder if someday, someone will have all this worked out on a plug and play app, with sliders so you can adjust your parameters and it will spit out a recommended cartridge, bullet, powder combo. People are so eager to build apps these days, it wouldn't surprise me if someone did something like this, if even just to compare cartridges against one another.

This seems to be making things more complicated than necessary.

Again, the analysis ends with an empty set, so the ONLY means to confine a result is to over-define the system - and then to what end? Are we naive enough to expect least recoil recoil energy will correspond with highest fps/grn? Add a pound of rifle weight, and the entire system is upturned. Change bullet weight, again, the entire system is upturned. So even in a restricted analysis, the exercise is trivial. If we analyze the cartridges based upon momentum (which is conserved in real world collisions) rather than kinetic energy (which is not), then we also again upturn the analysis…

It’s kind of akin to asking the most efficient size of jeans… well… smaller sizes require less material than larger sizes, but if the pants don’t fit because the size is too small, “efficiency” becomes meaningless. We can throw great big bullets downrange from cartridges like 45acp, with very little powder use and very little relative recoil - highly efficient… how excited are you by the prospect of hunting deer with a 45acp carbine?

Efficiency - in a multitude of definitions - just doesn’t matter much if at all in the context of cartridge performance for a given task.

 

[Howland937]

kind of akin to asking the most efficient size of jeans… well… smaller sizes require less material than larger sizes,

But leopard print stretchy pants fit nearly all sizes, so they're more efficient than jeans. In some cases, the additional stretching makes the spots bigger and more resemble giraffe print though.

Which reminds me that barrel life would also be taken into consideration in an efficiency quest, if a person is asking too much of too little.

 

[CoalTrain49]

I’m just happy to see a post from someone who recognizes the difference between “caliber” and “cartridge”.

We've lost our way. Even the so called guru gun writers have failed us. I guess they've never actually read the definitions in loading manual. Or maybe they just prefer the street dialect so they can connect with their readers.

 

[Newtosavage]

I don't know about most efficient, but efficiency plays a role in my choosing cartridges. But it didn't always. I hunted with 30-06 for the better part of my life, about 40 years. But about a dozen years ago moved to 308. Looking at some numbers, (my actual loads).

I can get 2900 fps with 150's using 47 gr of powder in my 308

I can get 3050 fps with 150's using 62 gr of powder in my 30-06. Thats about 4% more speed, 24% more powder and about 20% more recoil.

I can get 3300 fps with 150's using 80 gr of powder in a 300 WM. Compared to 308 that is 12% more speed, 42% more powder and almost double the recoil.

When you start looking at trajectory, retained velocity, and energy numbers down range the 30-06 and 300 WM don't offer me any real advantages until I start taking shots beyond 400-500 yards. Which is farther than I'm going to shoot anyway.

I sold the 300 WM and keep the 30-06 simply because it has too much history to sell. But I rarely shoot it anymore and every time I sit down to load for it the amount of powder I'm pouring into each case just seems huge compared to what I load in my 308 cases. That same pound of powder just goes a lot farther.

Now if someone NEEDS the power and has the skills to use it then you NEED to go with a less efficient cartridge. A 3/4 ton truck with a diesel engine isn't as efficient as a Prius. But if you need to move a load the Prius won't get it done.

After toting an '06 all over the mountains of Colorado a few years ago, and getting punished by it (in a 6.5 lb. rifle) on the range all fall, I drew the same conclusion. For the distances I plan to shoot, the .308 was plenty of rifle for me.

 

[Newtosavage]

This seems to be making things more complicated than necessary.

Again, the analysis ends with an empty set, so the ONLY means to confine a result is to over-define the system - and then to what end? Are we naive enough to expect least recoil recoil energy will correspond with highest fps/grn? Add a pound of rifle weight, and the entire system is upturned. Change bullet weight, again, the entire system is upturned. So even in a restricted analysis, the exercise is trivial. If we analyze the cartridges based upon momentum (which is conserved in real world collisions) rather than kinetic energy (which is not), then we also again upturn the analysis…

It’s kind of akin to asking the most efficient size of jeans… well… smaller sizes require less material than larger sizes, but if the pants don’t fit because the size is too small, “efficiency” becomes meaningless. We can throw great big bullets downrange from cartridges like 45acp, with very little powder use and very little relative recoil - highly efficient… how excited are you by the prospect of hunting deer with a 45acp carbine?

Efficiency - in a multitude of definitions - just doesn’t matter much if at all in the context of cartridge performance for a given task.

Well YOU know that, and I know that, but for someone getting into firearms hunting and looking at a dizzying array of choices, a $5 app that might help them select could be useful.

 

[lysanderxiii]

Lets compare 22 calibers since there is a huge range of sizes. I'll just use the fastest load for each listed in the hodgdon load data for a 50 grain bullet along with the listed powder weight.

22 swift, 4035 fps, 45.0 grains, = 89.6 fps per grain, 40.1 ft lbs per grain
22-250, 4001 fps, 43 grains, = 93.0 fps per grain, 41.3 ft lbs per grain
22 nosler, 3731 fps, 34.5 grains = 108.1 fps per grain, 44.78 ft lbs per grain
223 rem, 3505 fps, 28.5 grains = 122.9 fps per grain, 47.8 ft lbs per grain
221 fireball, 3202 fps, 19.8 grains = 161.7 fps per grain, 57.4 ft lbs per grain
22 hornet, 2713 fps, 13 grains = 208.7 fps per grain, 62.8 ft lbs per grain
22 magnum, (federal 50gr small game), 1530 fps, 5.2 grains = 288.6 fps per grain, 50 ft lbs per grain
22lr, (american eagle suppressor 45gr RN), 970 fps, 1.0 grains = 970 fps per grain, 94 ft lbs per grain

So even all the way down to 22lr we are still gaining efficiency. The only real outlier is the 22 magnum energy per grain, but that is because it runs at half the pressure of the centerfire rounds so the efficiency gain of being smaller wasn't enough to overcome the efficiency loss of being at a lower pressure.

That comparison only works if you used propellants with similar burn speeds and temperatures.

The most efficient cartridge will be the one with the largest ratio of charge weight to area under the pressure curve.